The serotonergic neural system of the brain has been shown to influence a variety of physiologic functions which manifest themselves in a variety of disorders such as Alzheimer's disease, cognition disorders, irritable bowel syndrome, nausea, emesis, vomiting, prokinesia, gastroesophageal reflux disease, nonulcer dyspepsia, depression, anxiety, urinary incontinence, migraine, arrhythmia, atrial fibrillation, ischemic stroke, gastritis, gastric emptying disorders, feeding disorders, gastrointestinal disorders, constipation, erectile dysfunction, and respiratory depression.
5-HT receptor modulators e.g., agonists, partial agonists, inverse agonists and antagonists, and/or selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, paroxetine, fluvoxamine, sertraline, lorazepam, imipramine, citalopram, and nortriptyline, may be used for the treatment of the above conditions, as well as for vasodilation, smooth muscle contraction, bronchoconstriction, brain disorders such as vascular disorders such as angina and migraine; and neuropathological disorders including Parkinson's disease and Alzheimer's disease. They also intervene in the regulation of the cerebral circulation and thus represent effective agents for controlling migraine. They are also suitable for the prophylaxis and control of the effects of occurrences of cerebral infarct (Apoplexia cerebri) such as stroke or cerebral ischemia. They are also suitable for the control of disorders of the intestinal tract which are characterized by disturbances of the serotoninergic system and also by disturbances of the carbohydrate metabolism. They are suitable for the treatment of gastrointestinal disorders including irritable bowel syndrome.
Trazodone controls 5-HT actions, and fluoxetine and fluvoxamine facilitate serotonergic neurotransmission via potent and selective inhibition of serotonin reuptake into presynaptic neurons. 3-Chloroimipramine inhibits both 5-HT and norepinephrine reuptake. Other compounds of current interest as antidepressants include zimeldine, bupropion and nomifensine.
Tegaserod, an indazole carbazimidamide that acts as a 5-HT4 agonist, has been approved for irritable bowel syndrome (Buchheit et al. J. Med. Chem. 1995, 38, 2331-2338; Buchheit et. al., J. Med. Chem. 1995, 38, 2326-2330).
The 5-HT4 receptors represent a member of the family of receptors with seven transmembrane (7TM) domains coupled to a G-protein which is positively coupled to adenylate cyclase. The 5-HT4 receptors are expressed in a wide variety of tissues, including the human brain and the rodent brain, the human, dog, pig and rodent gastro-intestinal tract, and the pig and human heart. In the mammalian brain, the 5-HT4 receptors contribute to dopamine secretion and regulate learning and long-term memory via the modification of acetylcholine release. In the peripheral tissues, the 5-HT4 receptors have proven to regulate gastro-intestinal tract motility, intestinal electrolyte secretion, adrenal secretion of corticosteroids, bladder contraction and atrium contractility.
The 5-HT4 receptors are involved in a wide variety of central and peripheral disorders, including cardiac arrhythmias and neurodegenerative disorders and more specifically Alzheimer's disease, cognition disorders, irritable bowel syndrome, nausea, emesis, vomiting, prokinesia, gastroesophageal reflux disease, nonulcer dyspepsia, depression, anxiety, urinary incontinence, migraine, arrhythmia, atrial fibrillation, ischemic stroke, gastritis, gastric emptying disorders, feeding disorders, gastrointestinal disorders, constipation, erectile dysfunction, and respiratory depression.
The development of 5-HT4 receptor modulators, e.g., agonists, partial agonists, inverse agonists and antagonists, may have therapeutic applications in the central nervous system for treating neuropsychiatric disorders associated with a dysfunction of the central dopaminergic system, such as Parkinson's disease, or for treating amnesic deficiencies as presented in patients suffering from Alzheimer's disease. Such medicines might also be useful for treating peripheral disorders such as irritable bowel syndrome, gastroparesia, urinary incontinence and cardiac arrhythmias. Selective, high affinity, metabolically stable 5-HT4 receptor modulators that possess good bioavailability, CNS penetration, and good pharmacokinetic properties, e.g., in vivo, are desirable.